Method to control the feeding amount in band sawing machines

ABSTRACT

Method to control the feeding amount in hydraulically controlled band sawing machines having a pivotable frame which supports the band saw, and a hydraulic cylinder for lifting and lowering the frame with respect to the material to be cut, comprising a hydraulic pressure control means for cylinder, valve means (preferably with a knife-edge shaped outlet) for controlling the quantity of hydraulic fluid reaching the cylinder, and at least one hydraulic connection, namely between the outlet of the control means and the inlet of the valve means.

r 3 a e Kiwi; States E [191 [11] 3 73,33 Aizawa 1 May i, 1973 [54] METHOD TO CONTROL THE FEEDKNG 1,390,469 9/1921 Stowell ..83/201.06 AMOUNT 1 BAND SAWING 2,601,576 6/1952 Wells et a1 ..83/201.06 MACHINES FOREIGN PATENTS OR APPLICATIONS [75] Invemo" Tsune Aizawa lsehara Japan 588,875 6/1947 Great Britain ..83/20L06 [73] Assignee; Amada Co, Ltd, T kyo Jap 265,586 3/1950 Switzerland ..83/20106 [22] Filed: 1971 Primary Examiner.l. M. Meister [21 Appl. No.: 107,162 Attorney-Cecily L. Frey Related U.S. Application Data [62] Division of Ser. No 710,339, March 6, 1968, Pat. 1571 ABSTRACT 3575974 Method to control the feeding amount in hydraulically controlled band sawing machines having a pivotable [30] FOB-mg Apphcauon Pnonty Dam frame which supports the band saw, and a hydraulic June 12, 1967 Japan 42 3724I cylinder for lifting and lowering the frame with respect to the material to be cut, comprising a hydraulic pres- [52] 11.5. C1 ..83/13, 83/201.06 sure control means for cylinder, valve means [51] Int. Cl. ..B26d U46 (preferably with a knife-edge shaped outlet) for con- [58] Field of Search ..83/20106, 201.05, trolling the quantity of hydraulic fluid reaching the 83/564, 647, 13; 188/319; 143/19 R cylinder, and at least one hydraulic connection, name- 1y between the outlet of the control means and the [56] References Cited inlet of the valve means.

UNITED STATES PATENTS 6/1922 Stowell ..83/201.06 X

4 Claims, 6 Drawing Figures Patented May 1,- 1973 3,730,033

4 Sheets-Sheet 1 Inventor Tsuuso mum Patented May 1, 1973 3,730,033

4 Sheets-Sheet 2 FIG. 2

Patented May 1, 1973 4 Sheets-Sheet 5 mm a I Inventor TSUNK) AIZAHA Patented May 1, 1973 4 Sheets-Sheet 4.

WVENTOR, 'rsuuao AIZA'HA METHOD TO CONTROL THE FEEDING AMOUNT IN BAND SAWING MACHINES This is a divisional application of Ser. No. 710,839 filed Mar. 6 1968, now U.S. Pat. No. 3,575,074 titled Apparatus and Method to Control the Feeding Amount in Band Sawing Machines.

This invention is concerned with a method to control the feeding amount, i.e., the cutting-in speed of band sawing machines.

In a conventional band sawing machine, well-known needle valves have been used so far as quantity control valves for the oil flow out of the hydraulic cylinder which controlsthe lowering of the frame for the band saw. Generally, however, the oil pipe of the needle valve is so narrow that viscosity changes greatly influence the oil flow due to friction with the pipe wall. For instance, oil flow is relatively small when oil temperature is low at the starting of the cutting operation, while on the contrary oil flow becomes more intensive when oil temperature is high. Thus there has been the problem that the cutting-in speed increases gradually inspite of the constant throttling effect of the quantity control valve.

As a second problem, conventional band sawing machines have been constructed basically under the technical concept that the total cutting load of the saw blade should always be kept constant; consequently, for instance, there has been the disadvantage that, in case when the cutting length becomes gradually shorter, the load per unit length increases and the cutting-in speed increases. Thus in case of thin materials the cutting-in speed increases too rapidly, causing damage to the saw blade, and in case when the cutting length becomes too long or a hard material is to be cut, the cutting-in speed decreases, causing the saw blade to wear at its edge, and making its life shorter. Furthermore, this influences negatively the efficiency of operation.

This invention is aimed at solving the above-mentioned problems. Firstly the outlet side of the control valve is formed into a knife-edge shape so as to lessen the influence of viscosity variation. Thus, the oil volume passing through the quantity control valve is always kept at a level to correspond to the opening of said valve irrespective of the variation of oil temperature, whereby the variation of the cutting-in speed is controlled.

Secondly a mechanism for controlling and reducing oil pressure is provided between the oil outlet of the cylinder, which controls the lowering of the frame, and the control valve so as to control the descent of the frame at a constant speed and also to reduce its pressure to secure stability of operation of the control valve. In modern band sawing machines of relatively high speed and big horse power, with saw blades of improved quality and high efficiency, it has been actually realized that controlling the cutting-in speed at a constant rate is more effective than maintaining the total cutting load a constant value.

Other objects and many of the attendant advantages of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description, when considered with the accompanying drawings, wherein:

FIG. 1 is a side elevation of a horizontal band sawing machine fitted with a control apparatus for practising the method of the present invention;

FIG. 2 is a side elevation of the essential parts of FIG. 1, on an enlarged scale, and serving as an explanation of the cutting load;

FIG. 3 is a sectional view showing the construction of the apparatus of FIG. 1;

FIG. 4 is a sectional view taken along line IV IV in FIG. 3;

FIG. 5 is a schematic detail view explaining the mechanism of the quantity control valve; and

FIG. 6 illustrates the function of the hydraulic system of the apparatus of FIG. I.

FIG. 1 shows a band-saw blade 7 mounted on a frame 5 which is pivoted at point I to a bed or base 3, the frame 5 being provided with a hydraulic cylinder assembly U (schematically shown in FIG. 2 with a simple oil or other hydraulic fluid circuit). It will be understood by those skilled in the art that reference to oil as a hydraulic fluid will be made herein only as a matter of example, and the term hydraulic assembly should be understood in its broadest sense.

FIG. 2 shows the blade 7 cutting a material M, with a simplified cutting-load distribution. P is the reactive force from the hydraulic fluid or oil flowing out of a cylinder 11, forming part of the assembly U, through a Total cutting difference between the torques at W and P, around the pivot 1 distance between the pivot 1,

and the center of cutting The descent of the frame 5 corresponds to the descending speed of the'piston 9, i.e., the fluid-flow speed from the orifice 13, which increases if P is raised or increased, and decreases accordingly if P is lowered or decreased.

Consequently, when the opening of the quantity control valve, i.e., the fluid-flow speed from the orifice 13 is kept constant, and the blade 7 is cutting with a constant feeding amount, and if then the cut length of the material M is increased or decreased, the cutting load is accordingly increased or decreased. Also, P, the fluid flowing out of the orifice I3 and the descending speed of the frame 5, i.e., the feeding amount tends to increase or decrease accordingly.

Also, if the strength of the material M increases or decreases, the cutting resistance will be respectively increased or decreased, and thus the cutting load will be similarly increased or decreased, acting on P and the fluid-flow speed, i.e., to decrease or increase respectively the feeding amount.

In FIG. 3 the parts generally indicated by letter A constitute a mechanism to control and reduce the oil or hydraulic fluid pressure. A hydraulic case 15 is fixed appropriately to a machine body or base 14. Numeral l7 identifies a working piston slidably mounted in a cylinder 19. Numeral 20 is a spring held between one end of the working piston 17 and the inside bottom of the cylinder 19. The surface of the piston 17 (shown at 21 and 23, respectively, in elevation and in section) slidably contacts the inside of the cylinder 19, and at a recessed portion 25 of the piston 17 an oil passage 27 is provided which connects an oil passage 29 in the hydraulic case 15, which is connected to the oil passage 13, a recessed clearance 31 between the recessed portion 25 and the cylinder 19, and a clearance 33 between the right-hand piston head 23 and the other bottom of the cylinder 19.

The oil or hydraulic fluid passage 29 is partly closed by the piston 23, and as shown in the drawing, its opening increases or decreases as the piston 23 moves to the right-hand or the left-hand sides.

The mechanism generally indicated in FIGS. 3 and by the letter B is a quantity control mechanism. In the inside of a cylinder 35, two quantity control hollow cylinders 37, 39 are fixably mounted with a common axis. As shown in FIG. 5, the opposite ends of the cylinders 37, 39 are partly in contact, and the rest forms opposite circumferential surfaces c, c with a clearance e therebetween, the latter clearance being zero at said contact point and gradually increasing to maximum at the position advanced by approximately 180, only to decrease thereafter gradually toward the zero value.

A working plunger 47 is rotatably mounted with a close fit to the quantity control cylinders 37, 39, and fixed by an appropriately graduated handle 45 (see FIG. 3; the graduation or dial is not shown).

The plunger 47 has an oil passage 49 in its center, with one end open to an oil chamber connected to an oil passage 51 and to the clearance 33. The other end of the oil passage 49 is connected to an opening 53 which is positioned to meet said clearance e.

A clearance 55 between knifeedges 41, 43 is connected to an oil tank T (see FIG. 6), on the one hand, and, on the other, to the cylinder 19 where the spring is contained, through an oil passage 57. Parts 59 are fixing pins for the cylinders 37, 39.

The function of the above-described mechanism shall now be explained with reference to FIGS. 3 and 6. Firstly, the opening of the quantity control assembly B is appropriately pre-set by means of the handle 45. Under certain working conditions, the opening of the oil passage 29 and the action of the spring 20 will keep the balance, and the oil or hydraulic fluid flowing out of the cylinder 11 is being pressed by the piston 9 back to the oil tank T through orifice 13, oil passage 29, clearance 31, oil passage 27, clearance 33, oil passages 51 and 49, opening 53, and clearance 55.

If then the cut length of the material M increases, the reactive force P is reduced as explained before and the down-stroke of the piston 9 inside the cylinder 11 is shown down, resulting in less oil'flowing through the passages 13, 29 to the clearance 31. The pressure inside the clearances 31, 33 is accordingly lowered, and the piston 17 is displaced to the right-hand side by means of the pressure of spring 20. Thus, the opening of the oil passage 29 is increased and the oil flow out of the cylinder 11 is increased, which helps the downstroke of the piston 9 and controls the decrease of cutting-in speed.

In a contrary sense, if the cut length decreases and the cutting-in speed increases, the down-stroke of the piston 9 is accelerated and the pressure inside the clearances 31, 33 is raised so that the piston 17 is displaced toward the left-hand side. Thus the opening of the passage 29 is narrowed and the down-stroke of the piston 9, and accordingly the increase of the cutting-in speed, is controlled.

It goes without saying that for materials of different hardness values, the mechanism functions in the same way as above to control the variation of the cutting speed.

As shown in FIG. 6, the oil pressure in passage 51, behind the pressure controlling and reducing mechanism A, is identified by P while the outlet pressure, on the other side of the cylinders 37, 39, is denoted P The oil pressure P, is already reduced by the above-described operations and is thus remarkably low as compared to the prior systems where the cylinder is directly connected to the quantity control valve. Therefore, even when a conventional quantity control valve is used, its mechanism and operation can be simplified. In particular, the above-described device connects the outlet of the quantity control mechanism B to the cylinder 19 where the spring 20 is contained, whereby the difference between the oil pressures P and P is kept substantially constant, thus stabilizing the function of the quantity control valve.

As above described, the inventive method consists, in one of its most important aspects, to control appropriately the descending speed of the frame 5 of the band sawing machine by providing a hydraulic passage or connection, to connect the oil passage 13 which controls the descent of the frame to any quantity control 'valve, through the pressure controlling and reducing valve A, and by decreasing or increasing, as the case may be, the oil flow into said valve accordingly, as the descending speed of the frame increases or decreases. This procedural arrangement is not anticipated or even suggested by previous devices and arrangements.

By this method, even when the cut length becomes shorter or the hardness of the material to be out drops,

the cutting-in speed does not increase suddenly and.

thus the danger of breaking the saw blade is avoided.

Also, even when the cut length becomes longer or the hardness of the material increases, the cutting-in speed does not suddenly decrease, and the saw blade is not subjected to excessive wear. Furthermore, a lower pressure in the quantity control valve improves its operation.

The function of the quantity control mechanism B shall now be explained in more detail. The oil or hydraulic fluid flowing out of the clearance e between the cylinders 37, 39, after passing through the pressure control and reducing mechanism A, the oil passages 51 and 49, and the outlet or opening 53, is substantially free from the influence of viscosity variation due to the variation of oil temperature, by virtue of the knife edges 41, 43 at the outlet clearance 55. It is therefore possible to keep the oil flow constant by pre-setting the handle 45 and to exactly control the feeding amount. Also, the same effect is obtained in the case where the oil passage or orifice 13 is directly connected to the quantity control mechanism B.

An oil passage 13a, connected to the orifice 13, communicates with conventional pressure or propelling means Pa to supply pressurized hydraulic fluid to a pipe connection 14a, having a check valve Va therein,

which allows the fluid to flow in one direction, namely from Pa toward the pressure head of cylinder 1 1.

When one cutting-off operation is completed, the valve Va is opened (means Pa is actuated by any conventional power source such as a motor) and the pressurized fluid is allowed to flow through the pipe 14a, oil passage 13a and then into the pressure head of the cylinder 11, causing upward displacement of the piston 9, which in turn results in the upward pivotal movement of the frame 5, whereby the machine is ready to receive a new material M to be cut.

It is noted that during the upward displacement of the piston 9 the fluid supplied by the supply source Pa is also allowed to flow into the pressure control mechanism A. causing the same to be automatically adjusted to a position corresponding to the pressure of the fluid. It is to be noted, however, that the fluid flow into the mechanism A does not interfere with the upward displacement of the piston 9.

After new material M is set into a cutting position the motor driving the pressure means Pa is stopped, and the apparatus will repeat the cutting cycle as above described.

It should be noted that the mechanisms A and B are only schematically shown in FIG. 2 while more details appear in FIG. 6, and a sectional illustration is given in FIG. 3. The oil tank T is shown in both FIGS. 2 and 6.

Furthermore, the above-described function and effect is also obtainable in the commonly known case where the oil passage is arranged to double-act on the piston.

It should be understood, of course, that the foregoing disclosure relates only to a preferred embodiment of the invention and that it is intended to cover all changes and modifications of the example described which do not constitute departures from the spirit and scope of the invention.

What I claim is:

l. A method to control the feeding amount in a hydraulically controlled band saw machine, comprising the steps of adjusting the pressure of the hydraulic fluid in a hydraulic cylinder with a control system, for selectively lifting and lowering a portion of a frame in the machine so as to pivot the frame with respect to the material to be cut, the frame supporting a band saw which operatively engages the material; controlling the quantity of the adjusted hydraulic fluid flowing through a valve cooperating with the cylinder; establishing a first hydraulic connection between the outlet of the cylinder and the inlet of the control system, and a second hydraulic connection between the outlet of the control system and the inlet of the valve; restricting at least one passage in cross-section, provided in the control system for the hydraulic fluid, by accelerating the action of the cylinder upon decrease of the cutting resistance of the material and upon increase of the cutting-in speed of the band saw, and vice versa; and maintaining the pressure of the hydraulic fluid at a constant value when the same leaves the control system.

2. The control method as defined in claim 1, further comprising the step of bypassing the hydraulic fluid from the outlet of the valve to a spring-biased side of a piston included in the control system.

3. The control system as defined in claim 1, further comprising the step of adjusting the outlet of the cylinder with respect to a transversal passage provided in the valve.

4. The control method as defined in claim 1, further comprising the step of providing a flow path for the hydraulic fluid from the cylinder to a storage tank by way of the control system, the second hydraulic connection and the valve, and back again. 

1. A method to control the feeding amount in a hydraulically controlled band saw machine, comprising the steps of adjusting the pressure of the hydraulic fluid in a hydraulic cylinder with a control system, for selectively lifting and lowering a portion of a frame in the machine so as to pivot the frame with respect to the material to be cut, the frame supporting a band saw which operatively engages the material; controlling the quantity of the adjusted hydraulic fluid flowing through a valve cooperating with the cylinder; establishing a first hydraulic connection between the outlet of the cylinder and the inlet of the control system, and a second hydraulic connection between the outlet of the control system and the inlet of the valve; restricting at least one passage in cross-section, provided in the control system for the hydraulic fluid, by accelerating the action of the cylinder upon decrease of the cutting resistance of the material and upon increase of the cutting-in speed of the band saw, and vice versa; and maintaining the pressure of the hydraulic fluid at a constant value when the same leaves the control system.
 2. The control method as defined in claim 1, further comprising the step of bypassing the hydraulic fluid from the outlet of the valve to a spring-biased side of a piston included in the control system.
 3. The control system as defined in claim 1, further comprising the step of adjusting the outlet of the cylinder with respect to a transversal passage provided in the valve.
 4. The control method as defined in claim 1, further comprising the step of providing a flow path for the hydraulic fluid from the cylinder to a storage tank by way of the control system, the second hydraulic connection and the valve, and back again. 